In the control circuits of some traditional types of automatic coffee machines, the self-turn-off function can be automatically activated through a special logic controller supplied by an electric power circuit on which an electric power supply deviator can be installed piloted by the logic controller itself.
In some known solutions wherein low voltage power supply of the logic controller is envisaged, the electric power supply of the controller has a transformer inside it that can lower the high input voltage in order to make it compatible with the low output voltage for the logic controller itself
One of the drawbacks that can arise consists of the fact that the logic controller stops working if it is not appropriately supplied during the time needed for the deviator to switch. This occurs because the low output voltage is lacking in the transformer at the same time as the high input voltage is lacking.